CST-171 Final Exam Review

Control Statements

100

What is printed to the screen? fahrenheit = 50 if fahrenheit > 90: print(“Heat warning!”) if fahrenheit < 30: print(“Cold warning!”)

Nothing!

200

Which lines will be executed if the if statement is true? if (a == 5): print("This one?") print("How about this one?") print("Maybe this one?")

The first two print statements

300

What is the difference between = and == in Python?

= is the assignment operator. It is used to assign a value to a variable. == is used to test for equality. a = 10 # assigns 10 to the variable named a if ( a==10 ): # tests if a currently contains a value of 10

400

Briefly describe how if ( a == 10 ): # statements else: # statements is different than if ( a == 10 ): # statements if ( b == 10 ): # statements

With an if-else combination only one block of statements will get executed. With multiple if statements it is possible, but not required, that all blocks of statements will be executed

500

True or False: When using if and elif a final else statement is required? if value < 0: print("\n You entered a negative number.") elif value == 0: print("\n You entered zero.") else: print("\n You entered a positive number.")

False

Loops

100

This loop executes how many times? for i in range(10): print(i)

10

200

What gets printed the first time this loop executes? for i in range(10): print(i)

0

300

What is the difference between a while loop and a for loop? Under what circumstances might you use one over the other?

for loops are called definite loops. They are used when we define in advance how many times we need to iterate. A while loop is an indefinite loop. It loops until a condition is true. There is no way to tell beforehand when this will occur.

400

What is the output of this Python code? a = 5 b = 10 while( a == 5 and b <12): print("Hello World") b = b + 1

"Hello World" will be printed twice. After two iterations b will have a value of 12 and the second while condition will no longer be true.

500

What is the output of this Python code? a = 5 b = 10 while( a == 5 and b <12): print("Hello World") b = b - 1

This is what is called an infinite loop. It will print "Hello World" forever!

Classes and Objects

100

Briefly define the difference between procedural and object oriented programming.

Object oriented programming uses classes and objects to model real-world entities. Programs are written as a set of interacting objects. Procedural programs execute sequentially from top to bottom.

200

True or False Python only supports procedural programming.

False

300

In object oriented programming ________ are used to represent an object's attributes (data values) and _______ are used to represent an object's methods (operations the object can perform).

variables and functions

400

Given the following Python code, what is the name of the class and how many objects are created from it? ba1 = BankAccount() ba2 = BankAccount()

The class name is BankAccount and two objects were created: ba1 and ba2

500

Encapsulation is an important property of objects. What is it?

All the data and operations of a real-world entity are self-contained. For example, with our BankAccount class, each object contained a name, a balance, and operations to deposit and withdraw money. This was part of the object and independent of other objects - we could update the balance of one bank account object without impacting any other bank account objects.

More Classes and Objects

100

What is the Python symbol used to call (execute) a method of an object? a.) The dot operator (period) b.) The hash tag operator (#) c.) The method operator (! on the keyboard) d.) The dash operator ( - on the keyboard )

The dot operator (period on the keyboard)

200

Given the following Python statement from cst171 import AssignmentThree What is the name of the class we are importing and what is the name of the file in which it is stored?

The from statement has the structure from filename import ClassName using this information we can determine that we are importing a class named AssignmentThree from a file named cst171.py

300

Class methods always contain "self". What does self represent and why is it needed? def withdraw(self, amount): self.balance = self.balance - amount

"self" tells the object to update itself and not some other object. This is how we enforce encapsulation. In the above example the self in the definition tells the object to perform the operation on itself. The self in the self.balance tell the object to update its balance and not another object's balance.

400

Given the following class initialization method, give an example of how you would create a MyClass object from it class MyClass: def __init__ (self, firstName, lastName)

obj = MyClass("First","Last")

500

Given the following Python statement obj.updateSomething() What two things can you conclude about obj?

obj is an object and it has a method named updateSomething

Hands-On

100

Create the following list fruits = ["apple","banana","coconut"] and write one Python statement to print coconut using the fruit variable.

print( fruit[2] )

200

Write a for loop that prints "Hello World" to the screen 20 times

for i in range(20): print("Hello World")

300

Write a for loop that prints the numbers from 0 to 20 to the screen

for i in range(20): print(i)

400

Create a class named MyClass with a method named test that accepts two numbers as inputs, adds them together, and returns the results (ignore the __init__ method for now)

class MyClass: def test (self, num1, num2): result = num1 + num2 return result

500

You are told that SomeClass has a method named "sample" that takes no inputs. Given obj = SomeClass() what would be the Python statement that executes the sample method on the object we created?

obj.sample()